PURPOSE: To investigate whether polycarbophil, a mucoadhesive polymer of the poly(acrylic acid) type, would improve the ocular delivery of topically applied gentamicin. METHODS: Two gentamicin formulations of this polymer (neutralized versus non-neutralized) and an aqueous control formulation in saline were administered to the pigmented rabbit eye. Drug concentrations in plasma, as well as in cornea, bulbar conjunctiva, anterior sclera, iris-ciliary body, aqueous humor, and vitreous humor, were measured by fluorescence polarization immunoassay. RESULTS: Both polymeric formulations increased the uptake of gentamicin by the bulbar conjunctiva two times. Drug penetration into the aqueous humor was observed with only the non-neutralized polymer, probably occurring via the conjunctival-scleral pathway facilitated by intensified contact between the mucoadhesive polymer and the underlying bulbar conjunctiva. CONCLUSION: Polymers of the poly(acrylic acid) type are potentially useful for improving topical antibiotic drug delivery, particularly when irritancy potential due to low pH can be overcome.